While they can, of course, do whatever they want, I am disappointed by the development of unnecessary peripheral functionality such as this.

I think that the resources put toward this endeavor could have been better spent on improving the performance of Firefox, or perhaps reducing its memory usage, or even fixing the numerous bugs that affect it. Firefox isn't as bad as it once was with respect to those things, but there's still much room for improvement.

Functionality that's useful to a comparatively small number of users should be prioritized well behind core functionality that affects basically all Firefox users.